1. Field of the Invention
The present invention relates to a probe card to inspect the electric properties of the micro electronic device. More particularly, the present invention relates to a probe card structure wherein, when the probes fabricated by etching the silicon substrate are mounted on the main circuit board, the assembly characteristics and the convenience of circuit connection are improved.
2. Description of the Related Art
Generally, during or after manufacturing an electrical circuit device such as a semiconductor integrated circuit device, or before attaching the lead frame to the device, the device should be inspected whether the device was manufactured according to the specifications, and whether the measured whole or partial electric properties coincides with the desirable electric properties for the designed device. The inspection device used to inspect the device is the probe station. A probe card is one of the main parts which are mounted on the probe station.
The conventional probe card (1) consists of 2 main parts as shown in FIG. 1 and FIG. 2. One part of the probe card (1) is a slender and sharp probe (1a) like a needle. Another part is a circuit board (1b) which structurally supports the probe (1a), and electrically connects the probe station (not illustrated) and the probe (1a).
The probe card (1) with such structure is fixed under the insertion ring which is supported by the head plate (5) of the probe device (2) as shown in FIG. 3. A work table (7) is installed below the probe card (1). The work table (7) may be moved 3-dimensionally (X, Y, Z axes). A semiconductor wafer (3) wherein the device to be inspected is fabricated is placed on the work table (7). The probe card (1) electrically connects the electric signal measurement equipment (not illustrated) in the probe station (2) to the electric pads (4) on a single or multiple devices.
Hereinafter, the conventional process of measuring the electric characteristics of the semiconductor device by using such probe station (2) is explained. First, the probe card (1) is fixed under the insertion ring which is supported by the head plate (5) of the probe station (2), and the semiconductor wafer (3) wherein the device to be measured is fabricated is fixed on the work table (7). Then, the work table (7) is moved in the direction of the X and Y axes, then align the position of the electric pad (4) of the device to be measured on the semiconductor wafer (3) with tip of the probe (1a) of the probe card (1) perpendicularly. Then, the work table (7) is moved in the direction of the Z axis to contact the probe (1a) with the pad (4). If the signal measurement equipment (not illustrated) of the probe device (2) outputs an electric signal for the measurement of the device's electric characteristics, then the electric signal is transmitted to the circuit board (1b) of the probe card (1) through the pogo pin (6). The electric signal is transmitted to the tip of the probe (1a) through the circuit board (1b)'s electric wiring (not illustrated), and thus, it is supplied into the device through the pad (4). After this, the electric response signal generated from the device is transmitted by reverse order of the above signal path to the signal-measuring equipment.
The conventional probe card is called the epoxy type or the tungsten needle type. This type of card is one that measures the electric characteristics of the device which is fabricated on the semiconductor wafer (3) by fixing a probe of tungsten which looks like a needle with a sharp tip to the circuit board (1b) using epoxy.
The manufacturing method of this type of probe card is disclosed in many patents such as U.S. Pat. No. 4,523,144, U.S. Pat. No. 4,799,009 and Korean Utility Model Patent No. 200,534. However, recently, semiconductor device's pads have sharply decreased in size and increased in density due to the high integration of the semiconductor devices. Now, it is common for pads less then tens of μms in size in array with spaced by μms in a device. Also a single probe card may be required to contain about 4,000 probes.
Because the tungsten probe is relative thick (thickness of hundreds of μms), it is very difficult to install the required number of probes to the probe card's circuit board to simultaneously measure multiple devices. It is also difficult to accurately position the probe. Moreover, because the probe is long and the probe's lengths are all different, the electric interference may occur when an electric signal is transmitted through the probe and it is difficult to control the electrical impedance without shielding. As a result, it is difficult to apply the conventional method to measuring high-speed devices such as the Rambus Dynamic Random Access Memory. Also, the scrubbing action of the probe on the pad of the device is large, often exceeding tens of microns due to long needle length and unevenness of the probe tip height. This can cause the probe tip to be located outside the pad after the scrubbing action.
New types of probe cards are being developed to overcome these problems. Requirements of the new card are many, and among them are fine pitch array, superior electrical characteristics and small scrub mark.
When manufacturing probes, it is important that each of the probes must make contact with the corresponding pad of the device that was fabricated on the semiconductor wafer to be inspected. Further, each of the probes must apply a predetermined range of pressure to the pad. Therefore, the tips of the probes must be arrayed uniformly, and have a good planarity. Further, each of the probes must have a predetermined value of elasticity. If the probes have elasticity to perform elastic deformation, the probe card can be used to conduct the required electric measurement, even though there is a small error in the planarity of the probe's tip or an error in the location of the device's pad, for example, if the device's semiconductor wafer wherein the device is fabricated is not completely flat and has a little distortion. The manufacturing method of these probes has been disclosed in the U.S. Pat. No. 4,961,052, U.S. Pat. No. 5,172,050, and U.S. Pat. No. 5,723,347. The inventors of the present invention have Korean Patent No. 319,130, No. 328,540 and U.S. Pat. No. 6,414,501 for the probe card where the microscopic cantilever probe fabricated on the semiconductor wafer is attached to the insulating circuit board.